When you replaced everything, did you properly service the bands?
Also, if the valve body was dropped and not filled prior to install (not an easy thing to do) it can take quite a while to refill everything. Last time I dropped mine, it took nearly 10 miles to get out of first.
Just take your truck at idle and keep switching between reverse, neutral and all the drive gears. Do this for 5 minutes at idle then again under light throttle. Then take it for some slow drives, and every now and then give it some gas, but let right back off after a second. It might take awhile, but eventually all the air will be expelled from the solenoids and pressure reservoirs and normal operation will resume. I strongly suggest adjusting the bands after this procedure to ensure proper operation.